In the technical field of support heads for video photographic apparatus, there are known heads in which the apparatus, when coupled to the head, can be oscillated with a high degree of precision about one or more axes of rotation defined on the head.
These heads comprise an adjustment mechanism, typically based on gearing, which causes the relative rotation of one or more components of the apparatus about one or more of the aforesaid axes. In particular, it is known a head comprising a first and a second body coupled together with the possibility of rotation about an axis of the head, and an adjustment mechanism which allows the user to cause this rotation by acting on an operating lever associated with one of the two bodies.
The adjustment mechanism typically comprises a reduction mechanism such that a rotation of the operating lever carried out by the user results in a rotation of much smaller angular amplitude of the first body relative to the second body.
Thus, it is possible to achieve extremely precise rotation of the apparatus, but, at the expense of the speed of rotation of the apparatus.
U.S. Pat. No. 5,589,903, in the name of the same Applicant, describes a support head comprising an adjustment mechanism allowing the user to disengage, when necessary, the gearing which engages the first body with the second body, in such a way that the rotation about the axis can take place freely without the need to rotate the operating lever. Thus the user can make a first very fast rotational movement to reach an approximate position, and then, having put the adjustment mechanism back into the engaged condition, can make a second, fine, rotational movement to reach the desired angular position in a precise way.
In the support head described in U.S. Pat. No. 5,589,903, the adjustment mechanism is disengaged by rotating an appropriate ring nut mounted coaxially on the operating lever, which moves the operating lever translationally away from a pinion mounted on the other body. The ring nut is rotated by the user in opposition to the elastic action of a spring which tends to keep the adjustment mechanism in mutual engagement.
However, the system described above has a few drawbacks, including the fact that it is less intuitive for the user, who, for example, receives no immediate indication of the direction in which the ring nut must be rotated to disengage the adjustment mechanism.
Moreover, in order to prevent the unbalancing of the weight of the apparatus due to the rotation that takes place about a non-vertical axis (for example, about the horizontal axes known as the level or the tilt axes) from causing an undesired movement of the operating lever, thereby disengaging the adjustment mechanism and causing the apparatus to fall by free rotation, the spring must have a relatively high elastic constant, to ensure that the adjustment mechanism is effectively kept in the engaged condition even in the presence of unbalanced loads.
However, this requires the user to make a considerable effort, both to rotate the ring nut and to keep it in the disengaged position against the elastic action of the spring.